A parathyroid hormone-related peptide (hereinafter, PTHrP) is a protein produced by a tumor, which is a major causative agent of humoral hypercalcemia of malignancy. A PTHrP induces humoral hypercalcemia of malignancy (hereinafter referred to as “HHM”), which is produced by tumor, by promoting bone resorption and renal reabsorption of calcium. Such an effect is known to be induced by a peptide site (referred to as PTHrP (1-34)) of the sequence of amino acids 1 to 34 on the N terminus of PTHrP through its receptor, a PTH/PTHrP receptor (J. Bone & Mine. Res. (1993) 8, 849-860). Currently, calcitonin and bisphosphonate preparations having an inhibitory action on bone resorption are used to treat HHM. However, since the progress of HHM is so rapid as to significantly deteriorate the QOL (Quality of Life) of patients with terminal cancer, development of a more effective therapeutic agent to respond to each cause has been awaited.
PTHrP has been suggested to have biological activity also at peptide sites other than PTHrP (1-34) (described in Naokazu NAGATA; Table 2 of CLINICAL CALCIUM, 5(3), 103-106, 1995). However, it has not yet been known that a peptide site (referred to as PTHrP (34-53)) corresponding to the sequence of amino acids 34 to 53 on the N terminal side of PTHrP produces an effect to stimulate cell proliferation.